Electron tube system



April 4, 1939. 4 R, URTEL 2,153,216

ELECTRON TUBE SYSTEM Filed March 17, 1936 .5 I g 7 q INVENTOR PUDOLF 7' EL BY W ATTIORNEY Patented Apr. 4, 1939 UNETE ST E GE ELECTRON TUBE SYSTEM many Application March 1'7, 1936, Serial No. 69,319 In Germany March 26, 1935 4 Claims.

The present invention relates to a safety device for protecting the luminous screen of cathode ray tubes intended for television receivers in particular, against damage by the cathode ray. If

5 for instance, for any reason the relaxation apparatus of a television receiver is put out of operation, the steady ray would cause burning or at least fatigue of the screen at the impinged place. The danger is especially great for instance in cathode ray tubes used for projections. In accordance with the invention, therefore, a device is proposed for the automatic blocking of the cathode ray at a dropping out of the relaxation device.

The device according to the invention is based upon the fact that in almost every line skip apparatus, circuits are present in which successions of current impulses occur. A CR-element inserted in such circuit furnishes a drop of the direct potential through the resistor, while the alternating components pass across the condenser C. In accordance with the invention this direct voltage source is placed in such manner that it opposes a blocking biasing potential at a control electrode of the cathode ray tube so that while the relaxation device is in operation, this control electrode permits passing of the cathode ray. When the relaxation device fails, the direct potential drop through the resistor opposing the blocking action will no longer be produced whereby the cathode ray will be blocked.

An example of an embodiment of the invention is represented in the drawing. The cathode ray tube B has modulating potentials fed to the grid G and the cathode l3 through a series connection M comprising a parallelly connected resistor R. and condenser through the biasing battery EG. The resistor R. and condenser C likewise form part of the cathode H return circuit of the gaseous discharge tube E, the anode 9 of which tube is fed through a series resistance I by a source of positive Voltage connected to the terminal 5. Connected between the anode 9 and the common terminal of the bias battery EG and the condenser C is a condenser K. A source of synchronizing impulses I is connected to the terminals l and 3, the connection 3 serving to feed the synchronizing signals to the control electrode ST of the tube 9. Herein is E, a gaseous discharge tube forming in connection with the charging condenser K the essential constituents of the relaxation device synchronized by synchronizing impulses across a control electrode St and cathode I l by way of the resistance R and the terminal I. The D. C. component of the impulses produced passes across the resistor R. The drop in direct potential produced through resistor R has a direction opposite to that of the blocking potential for the cathode ray tube and which is furnished by the bias battery Eg, so that in this manner the said blocking potential will be eliminated and the cathode ray permitted to pass through the electrode G. The condenser C is suitably chosen in such manner that the voltage drop will be low, and that no appreciable additional influence upon the biasing potential of the electrode G will be produced by the A. C. component during the operation of the relaxation apparatus. The impulses for modulating the ray may be applied at M, or may be brought to act upon the cathode ray across a separate control electrode not shown. The electrode G may as above explained, as ordinary control electrode either receive a resultant negative potential during the operation of the relaxation apparatus, or it may be a space charge electrode with a resultant positive potential.

What I claim is:

1. In a signalling system wherein is provided a cathode ray tube having a source of electrons and a control electrode and a saw-tooth oscillator, the method of operating which comprises the steps of supplying modulating potentials to the control electrode, biasing the control electrode to cut-off potential, and counteracting the cutoff potential biasing of the control electrode only when the saw-tooth oscillator is operating.

2. An electron tube system, wherein is provided a cathode ray tube having a beam of electrons and a control electrode for regulating the intensity of said beam of electrons, the method of operating, which comprises supplying a biasing potential to the control electrode to suppress the beam of electrons, superimposing upon said biasing potential modulating potentials, supplying a source of oscillatory energy, and counter-balancing the biasing potential by a portion of the produced oscillatory energy.

3. In a cathode ray tube system, a cathode ray tube having means to produce a beam of electrons, control means to regulate the intensity of the beam of electrons, means to supply to said control means a source of voltage to suppress the beam of electrons, means to supply to said control means modulating potentials, means to develop saw-tooth wave energy, means to derive a portion of the developed saw-tooth energy, and means to supply the derived portion of developed energy to the control means in opposite polarity relation to the source of voltage.

4. In a cathode ray tube system, a cathode ray tube having a source of electrons and a control electrode, a series combination of a source of voltage, modulating potentials and a parallelly connected resistance and condenser connected between the source of electrons and the control electrode, and means including a saw-tooth wave oscillator connected across said parallelly connected resistor and condenser for supplying energy thereto in opposite polarity relation to the source of voltage.

RUDOIF URTEL. 

